The use of lasers for producing low temperature polycrystalline silicon (LTPS) layers on glass substrates is an important technological advance in the manufacture of flat panel displays. Existing systems commonly use a high power excimer laser in cooperation with appropriate optics to create a long and narrow line of laser radiation on a layer being crystallized. The radiation intensity in the beam line is sufficient for melting and subsequent crystal re-growth in a silicon layer, resulting in much improved electrical parameters of the film.
Excimer lasers, however, have high initial capital costs and high running costs compared with solid-state lasers. This has prompted research into possibilities of using solid-state lasers in place of excimer lasers in silicon crystallization. Q-switched frequency-doubled solid-state lasers having an output wavelength of about 532 nm have proved useful in producing LTPS films. However, scaling such a laser to the required average power levels for crystallization (greater than about 100 Watts at a minimum and preferably greater than 1 kilowatt), while preserving the high beam quality is not a simple task. This requires technical improvements in the laser design that are not readily feasible, and leads to a costly system. Presently, such lasers are commercially available with output power levels of less than 200 watts (W), more commonly about 50 W. Additionally, such lasers typically output relatively short pulses ranging from few nanoseconds (ns) to several ten nanoseconds. A desired optimal pulse duration is several hundred nanoseconds. Therefore, there is a clear need for a high-average-power, pulsed, solid-state laser source that is cost efficient, scalable to required power levels, and has a pulse duration at least significantly greater than that available from prior-art commercially available Q-switched lasers.